Municipal and county water departments are frequently confronted with unauthorized use of fire hydrants by members of the public who, on occasion, open the valves of the hydrants to obtain water to cool-off on hot days or for the purpose of filling tank trucks with fresh water which is then sold for various purposes, such as filling swimming pools. In cities, open fire hydrants can result in a drop in water pressure to customers and can occasionally endanger a community by reducing the availability of water necessary to fight fires.
In attempts to secure fire hydrants from unauthorized use, fire companies have employed locking devices such as the magnetic valve lock of U.S. Pat. No. 4,620,428. The particular valve lock disclosed in the '428 patent utilizes a magnetic detent which couples the valve operating nut of the fire hydrant to a sleeve which is normally freely rotatable with respect to the nut. The magnet is attracted by a second magnet permanently mounted in a wrench which cooperates with the sleeve to rotate the sleeve. With the help of magnets, sledge hammers and other nefarious devices, water thieves and vandals are increasingly able to defeat magnetic locking devices such as that shown in the '428 patent. Accordingly, there is a need for improvement in magnetic locks for fire hydrant operating valves which minimize the effectiveness of various techniques employed by unauthorized users to operate the valves.